Conventionally, a fuel vapor treatment apparatus has been known, which treats fuel vapor generated in a fuel tank by introducing the fuel vapor into an engine. In the fuel vapor treatment apparatus, the fuel vapor is temporarily adsorbed by a canister. When a purge valve is opened according to a driving condition of the engine, the fuel vapor is suctioned into the engine.
In a fuel vapor treatment apparatus shown in JP 2006-177199A, when an engine is shut down, a purge valve disposed in a purge line is closed and a pressure drop in the purge line is detected to determine whether a fuel leak from the purge line occurs. When no fuel leak occurs, the pressure in the purge line falls below an atmospheric pressure. When a fuel leak occurs, the pressure in the purge line converges to the atmospheric pressure. Based on this, a determination of fuel leak is performed.
Although the fuel vapor treatment apparatus shown in JP 2006-177199A can determine whether a fuel leak from a purge line occurs, it cannot determine whether a clogging of the purge line occurs. For example, even if a fuel leak from a purge line occurs, it is determined that no fuel leak occurs in a case where the purge line is clogged between a leak portion and a pressure sensor. Therefore, it is required to determine whether a purge line is clogged in addition to a determination of a fuel leak.